why the need for hcn-m ? more accurate data through: redundant sensors near real time diagnostics...

Why The Need For HCN-M ?

More Accurate Data Through:Redundant Sensors

Near Real Time Diagnostics

Time Resolution of Five Minutes vs The Current Daily

Human Interaction With Weather Observations Has Been The Backbone Of The Historical Data Sets For More Than 100 Years

Temperature Measurements

Louvered Shelter For Ventilation Of Temperature Sensors And Protection From Direct Solar And Terrestrial Radiation

Used By Both Primary And Cooperative Stations For More than 100 Years

Redundant sensors, more than one thermometer in each shelter

Minimum Thermometer

Maximum Thermometer

Thermograph

Primary Weather Stations Were Also Equipped With Two Additional Matched Thermometers For Determining The Dew Point Temperature And Relative Humidity

Redundancy Of Temperature Measurement Was Lost In The 1980’s With Conversion To A Single Automated Electronic Sensor Called “The MMTS”.

Lightning, the worst nightmare for electrically operated temperature sensors. Those same electronic temperature sensors are also subject to salt air corrosion, and insect nests. (See next slide)

Data From An “MMTS” Temperature System At A Cooperative Station

Ventilation problems and slippage of the mechanically driven clutch read-out of the automated temperature sensor at the Asheville Airport compromised the readings from the site for more than 20 years. (See Next Slide)

Even Primary Airport Weather Stations Are Not Exempt From Single Sensor Failures

Modernization Of The Equipment At The HCN Test Sites Uses The Proven Methodology Of The Past,

Redundant Sensors

AL Greensboro HCN-M (County Jail)AL Greensboro HCN-M (County Jail)32.7 N 87.6 W 273’

March 16, 2007

Geonor All-Weather Precipitation Gage With Three Independent Sensors And Protecting “Wind Fence”

Three Temperature Sensors in One Shield Equipped With Two Fans

Solar Panels to Power the Station

Temperature Traces of The Three Thermometers

Fan Ventilation Rate (R/S)

Back-Up Fan

Precipitation Measurements

Snow Clogged Tipping Bucket Gage

The Easiest Design Is Not Always The Best

Tipping Bucket Mechanism Does Not Measure Snow Events, And Frequently Under-Reports Intense Rainfall

Snow Sticking to The Un-Heated Chute of a Weighing Precipitation Gage

Same Gage Type Clear of Snow When Equipped With a Heater

Chute Temperature Rises When Heater is Activated

Air Temperature

Traces of Three Precipitation Sensors

Wetness Sensor Readings